In the domestic reserves of fossil fuels, coal is of 96.7%, oil is of 1.6%, and natural gas is of 1.7%, so the proportion of coal in the domestic energy consumption is always of about 70%. Because the reserves of oil and natural gas are not very abundant, since 1993 China had become an oil import country from an oil export country with yearly increasing import quantum, and in 2007 the net crude oil import quantum of China had been up to 177.57 million tons.
Presently, oil is the main fuel in domestic industries such as oil recovery, glass industry, ceramic industry, mechanical industry and the like at a yearly oil consumption of about 60 million tons. If coal could be used regarding this oil consumption, a benefit of more than 220 billions RMB could be expected, furthermore, a sum of foreign exchanges of about 43 billion USA$ for importing said oil could be saved. And in the world the sum of oil consumption in above-mentioned industries is as much as scores times of that in China.
In July 2007 International Energy Agency warned that the whole globe will encounter a crisis of oil supply in five years and at that time the oil price will be increased to a new record. In May 2008, the oil price was up to 130 USA$ per barrel.
One feasible way to cope with the “crisis of oil supply” is to recover the abundant heavy oil, which had been ignored in the past, however, during the “heavy oil thermal recovery” lots of steam at elevated temperature and pressure need to be injected into oil wells. And so far in the world all of the steam injection boilers or heating furnaces for heavy oil thermal recovery burn oil or natural gas as fuels, which comprise 8-12% of the recovered oil production.
In contrast, in the world coal reserves are much more abundant than oil reserves, but the coal price is less than one fifth of the oil price. Thus, using coal instead of oil, particularly those oil fuels in above-mentioned industries, will bring about significant economic and social benefits. However, in comparison with oil, coal has poor combustion properties, which are far from technical requirements in steam injection boilers, ceramic and glass kilns as well as kilns for heat-treating metals in mechanical industry. Thus, a lot of technologies are needed for using coal instead of oil.
It was reported that in the world most of the gas-burning boilers burn high calorific value gas fuels such as natural gas, liquefied gas and the like having a lower heating value above 32 MJ/Nm3 to obtain a stable combustion, and hot low calorific value gas is rarely used; furthermore, in the world most of the gas-burning boilers use positive pressure combustion systems at high pressure, double-normal temperature and small volume, for instance, a combustion system wherein the gas is at a pressure of more than 2500 Pa (gauge), the pressure inside the furnace is positive, the gas consumption volume for each burner is less than 3500 m3 per hour as well as both the gas and the combustion air are at normal temperature, so that to ensure homogeneous mixture between the gas and the combustion air to obtain a stable combustion.
One way for using coal instead of coal is using coal-derived gas instead of oil, for instance, Chinese patents ZL89103246, ZL94225393 and ZL99248296 etc disclosed the technology about gas-generated furnaces and coal gasification. However, there are a few reports about the process and apparatus for burning coal-derived gas instead of oil fuel for heavy oil thermal recovery, that is to say, such technologies are far from established yet.